A touchscreen panel, which is a device for inputting user's commands by touching letters or figures displayed on the screen of an image display device with a human finger or other touch means, is generally attached to an image display device. The touchscreen panel converts the touch location into electrical signals. The electrical signals are used as input signals.
Known methods for implementing a touchscreen panel include a resistive-type method, a photo-sensitive method, and a capacitance method. The touch panel with the capacitance method senses the change in capacitance formed by a conductive sensing pattern with another peripheral sensing pattern or ground electrode, etc., when a finger or object makes contact, and converts a contact location into an electrical signal.
FIG. 1 is an exploded plan view illustrating an example of a capacitive touch screen panel.
Referring to FIG. 1, a touchscreen panel 10 includes a transparent substrate 12, and a first sensor pattern layer 13, a first insulating layer 14, a second sensor pattern layer 15, and a second insulating layer 16 formed in order on the transparent substrate 12, and metal wiring 17.
The first sensor pattern layer 13 may be connected along the lateral direction on the transparent substrate 12, and may be connected with the metal wiring 17 in the unit of rows.
The second sensor pattern layer 15 may be connected along the column direction on the first insulating layer 14, and disposed alternately with the first sensor pattern layer 13 so as not to overlap with the first sensor pattern layer 13. Also, the second sensor pattern layer 15 is connected with the metal wiring 17 in the unit of columns.
When a human finger or touch means touches the touchscreen panel 10, the change in capacitance according to touch location is delivered to the driving circuit through the first and second sensor pattern layers 13 and 15, and metal wiring 17. Also, the touch location is identified as the change in capacitance thus-delivered is converted into an electrical signal.
However, each sensor pattern layer 13 and 15 of the touchscreen panel 10 should have a pattern made of transparent conductive materials such as indium-tin oxide (ITO), separately, and include an insulating layer 14 between the sensor pattern layers 13 and 15, which results in an increase in thickness.
Also, since touch detection is possible only after accumulating the capacitance changes minutely generated by touch several times, the capacitance change have to be detected with high frequency. Further, in order to sufficiently accumulate change in capacitance within a predetermined time, metal wiring for maintaining low resistance is required. Such metal wiring makes the bezel at the edge of the touchscreen thick and causes an additional mask process.
In order to solve this problem, a touch detection device was suggested as illustrated in FIG. 2.
The touch detection device illustrated in FIG. 2 includes a touch panel 20, a driving device 30, and a circuit board 40 connecting them.
The touch panel 20 is formed on a substrate 21, and includes a plurality of sensor pads 22 arranged in the form of polygonal matrix, and a plurality of signal wirings 23 connected with the sensor pads 22, respectively.
For each signal wiring 23, one end is connected with the sensor pad 22 and the other end extends to the bottom edge of the substrate 21. The sensor pad 22 and signal wiring 23 may be patterned on a cover glass 50.
The driving device 30 selects the sensor pads 22 one at a time, and measures the capacitance of the corresponding sensor pad 22. Accordingly, it detects whether touch is occurred.
Meanwhile, the touch detection device may be laminated on a display device or may be built-in. The display device may include a backlight, a polarizing plate, a substrate, a liquid crystal layer, a pixel layer 60, etc. Among them, a pixel layer 60 will be explained with regard to an embodiment of the present invention.
The pixel layer 60 is a color filter formed on a surface (a top surface or a bottom surface) of the liquid crystal layer for displaying an image. Colors may be implemented in a liquid crystal display with a pixel unit of red, green and blue (hereinafter, referred to as R, G and B). In this case, the pixel layer 60 includes a plurality of pixels including sub-pixels of R, G and B. Here, the liquid crystal layer includes an upper substrate, a lower substrate and liquid crystal, and generates contrast by modulating light (e.g., arrows illustrated in FIG. 2) from the back light to display the image.
As illustrated in FIG. 2, in the touch screen panel 20, each signal wiring 23 is arranged with a structure being connected to the bottom edge of the substrate 21, which makes deviation in a gap between the sensor pad 22 and the signal wiring 23. For example, in the case of the sensor pads located uppermost, since each signal wiring is arranged to be connected downwardly, the gap between the sensor pad and the signal wiring is wide. In comparison, in the case of the sensor pads located lowermost, the signal wirings connected to the sensor pads located in the top are arranged in areas adjacent to each other, and thus the gap between the sensor pad and the signal wiring becomes relatively narrow compared to the sensor pads located in the top.
That is, the gap between the sensor pad 22 and the signal wiring 23 may be different. Due to this deviation, there are problems in that scattered reflectivity of light emitted from a backlight varies depending on an area, and a difference in gap between the sensor pad 22 and signal wiring 23 may be stood out from outside.
FIG. 3 is an enlarged view illustrating a part of top surface of a conventional touch display device. In this case, FIG. 3 selects the pixel layer 60 and signal wiring 23 from the structure where the touch detection device is laminated, illustrated in FIG. 2, and enlarges the top surface overlapping the two constituents.
As illustrated in FIG. 3, the signal wiring 23 arranged in the same form as in FIG. 2 overlaps with the pixels arranged in the matrix form of the pixel layer 60 to be parallel to the column direction. In the case of pixel ‘A’ including sub-pixels of R, G and B, the signal wiring 23 overlaps a part of sub-pixel R and all of sub-pixel G in the column direction.
Although each signal wiring 23 in FIG. 3 is illustrated to overlap with a part of sub-pixel R and all of sub-pixel G, actually, there is a difference in gap between the signal wirings 23 according to the arrangement location (e.g., top or bottom). Thus, it is of course that areas of sub-pixels of R, G and B overlapping with the signal wiring 23 are different for each pixel. For example, when a specific signal wiring overlaps with a part of sub-pixel R and all of sub-pixel G, but another signal wiring overlaps with a part of sub-pixel G and all of sub-pixel of B, the portion overlapped by the signal wiring and the portion not overlapped by the signal wiring are different for each pixel, and thus the area of sub-pixels of R, G and B overlapping with the signal wiring 23 becomes different, either.
Due to this, each pixel differs from each other in terms of color temperature which each pixel generates according to light transmittance of the signal wiring 23 overlapped on each pixel. Accordingly, a difference in the sense of color is generated at any location. This causes a problem in that a pattern may be recognized with naked eyes due to a rainbow effect or Moire phenomenon of being scattered into rainbow light in all or a part of the touch panel.